Mathew, as a fellow coder and engineer turned into a business owner, you have to think about a few things:

What you believe your market is (professional developers) and what you think your product is (a professional tool) is at first, only what other people think it is based on their perception.

I looked at your project/GitHub, I am qualified to attest that your project is indeed a professional project and that professional developers would want to use it, but it took me 18 years to build up knowledge, and 15 minutes to browse your resources.

You are indeed a very professional engineer (judging from the above and your online presence), but, are you also a professional designer? a brand manager? You may not think so, but those professions are also things people spend their lives to perfect, just look at the amazing run-down by @Rafael

As an engineer, we are biased to think we can do everything ourselves, that's a good thing, but you have to let go and delegate some tasks as you grow your business/project, this is one of those.

Every single awful brand/images for OSS and proprietary tools out there are invariably a result of the project owner, an engineer, thinking they can fire up Gimp during a weekend and come up with a nice logo, their psyche takes over and they are unable to let go, and then we wonder why business owners are not buying it (our tool/OSS), well, business owners are not engineers (for the most part), all they have to evaluate your professionalism is your cashflow, logo, and brand, precisely to things OSS projects don't have.

My suggestion to you: delegate!, buy @Rafael's design, or go here: https://99designs.com.au create a "contest", put down the $350, let the engineers of branding do their thing, you will LOVE your new logo, and then focus on the tasks where you can apply your skills more efficiently.

Unfortunately, yes, your new logo is dull, generic and unmemorable, also, why on earth would you make a rubber duck grey and un-rubbery? A rubber duck is a toy for children, that is the power of image, people expect things to be in a certain way, or they get confused and unconsciously run away from your product.

The old design was actually better because it was giving a message: within 5 seconds you could understand it is a tool to make coding easier if you are dealing with VBA, the color is vibrant, and everybody loves a smiley, yellow rubber duck taking a swim, it sends an image of "fresh", "playful" and "easy".

See the problem? You took away all the good things about your old logo, now you are left with a generic word using a generic font with a generic silhouette, no meaning, message or color (what's worse, colour grey is associated with depression, it is the only color that sends no signal to our brains, that's why people will mention "dull").

And, you are approaching the problem as an engineer, thinking you can "objectively quantify" the design process, you can't, it's a form of art, there are "methods", but no design method is built on mechanics, it's like writing music (as opposed to reading music from the pentagram).

I apologize if I come as being rude, I'm trying to be objective, design/branding/color/psychology are fields that I enjoy reading/learning about, but it is better to hire the expert when you have to get the job done.